After "do not call" lists became popular, more than 90 percent of people who signed up reported fewer annoying telemarketing calls. Now, privacy advocates are pushing for a similar "do not track" feature that would let Internet users tell Web sites to stop surreptitiously tracking their online habits and collecting clues about age, salary, health, location and leisure activities.

That proposal and other ideas to protect online privacy are setting up a confrontation among Internet companies, federal regulators, the Obama administration and Congress over how strict any new rules should be. In the next few weeks, both the Federal Trade Commission and the Commerce Department are planning to release independent, and possibly conflicting, reports about online privacy. Top Commerce officials have indicated that the department favors letting the industry regulate itself, building on the common practice of user agreements where companies post their privacy policies online or consumers check a box agreeing to abide by them. Top trade commission officials, however, have indicated they are exploring a stricter standard, one that requires a "do not track" option on a Web site or browser similar to the "do not call" lists. The two agencies have even tangled over which will release its report first, a decision that could set the tone for the clash to follow. People close to the talks say that, at least for now, the Commerce Department has been given the nod, provided it can complete its report soon.